1. Field of the Invention
The present invention is directed to tape guides for guiding the tape in a reel-to-reel data tape cartridge, and more particularly, to a tape guide module containing a pair of tape guides configured to provide a tape guide adjacent to each side of a read/write zone in a data cartridge.
2. Description of the Related Art
The belt-driven data tape cartridge of von Behren, U.S. Pat. No. 3,692,255 has become a standard interface with computers where rapid acceleration and deceleration of the tape are required. In these reel-to-reel tape cartridges, an elastic driving belt extends along a belt path around corner guide rollers positioned adjacent the tape reels, contacts the tape on the reels, and drives the tape from reel to reel. A tape path extends between the reels and along one edge of the cartridge across a cutaway portion providing access to the tape by a transducer such as a magnetic read/write head which is a part of a tape drive which receives the cartridge. The tape path is defined by a guide pin, a pair of tape guides, and in some cartridges, a pair of tape wrap pins. One tape wrap pin is positioned between each reel and the adjacent tape guide to deflect the tape from a straight line path between the tape supply on the reel and the tape guide. This increases the frictional coupling between the tape and the tape wrap pin as the amount of tape wound on the reel increases and helps to maintain constant tape tension at the magnetic head.
Likewise, direct drive reel-to-reel cartridges have a tape path that extends through a cut-away portion on a cartridge. The cutaway portion defines a read/write zone where the tape is coupled with read/write heads in a tape drive.
In both belt-driven and direct-drive tape cartridges, the allowable tape speed and storage capacity (i.e., data density) increase with the accuracy at which the tape is coupled with the read/write heads. Therefore, further improvements in tape guide alignment has a direct positive impact on tape drive performance.
Both direct-drive and belt-driven tape cartridges must meet minimum tape tension specifications while simultaneously maintaining minimum drive force specifications. The tape tension must not fall below a certain level as the tape passes from reel to reel or contact between the read/write head and the tape will be insufficient. The minimum achievable tape tension should be sufficiently high to ensure proper cartridge operation. Similarly, the maximum required frictional drive force should be as low as possible to enhance cartridge operation within the power limitations of the drive motor. Thus, there is a limitation on the frictional drive force. The frictional drive force is that portion of the drive force which affects power loss at the interface between the backside of the tape and the tape guide. Minimizing the frictional drive force and improving tape tracking can be accomplished by minimizing the friction at the interface between the tape and the tape guides, which accounts for approximately one-third of the drive force in a data cartridge.
Early tape guides were made of a plurality of separate components staked together by a rivet. Upper and lower flanges or washers were fastened on the ends of a tape guide spacer. However, this system of assembly was subject to imprecise operation over time.
Injection molded plastic parts, while mass producible, do not guarantee durability, non-shedding, holding tight tolerances, or maintaining rigidity during use. Additionally, static build-up and dust collection are associated with dielectrics.
The current generation tape guides are made of a single piece of material that is machined, ground, or cast from a solid mass, such as non-magnetic stainless steel. This single piece construction requires that the tape guide be machined to accurately maintain the distance between the flanges and the overall part. Using stainless steel as a material for precision tape guides has resulted in expensive parts, due to the limited number of methods available for working stainless steel.